This invention relates to an auxiliary lighting controller for a lighting system.
An auxiliary lighting system may illuminate an auxiliary lamp to supplement a high intensity discharge (HID) lamp from the time that the HID lamp is activated until the HID lamp achieves full illumination, which may require several minutes. Whenever the HID lamp is deenergized by, for example, a momentary power failure, the HID lamp requires several minutes to cool off before it can be turned back on to provide illumination.
A circuit to control an auxiliary lamp may use a current transformer to sense the HID lamp current in order to determine whether the HID lamp is xe2x80x9con.xe2x80x9d The current transformer actuates a mechanical relay to provide power to the auxiliary lamp as appropriate.
In one general aspect, a lighting system includes a primary lamp circuit, an auxiliary lamp circuit, and an auxiliary controller. The auxiliary controller is connected between the primary lamp circuit and the auxiliary lamp circuit and is operable to sense a voltage of the primary lamp circuit. The auxiliary lamp circuit includes an auxiliary lamp. The auxiliary controller operates to extinguish the auxiliary lamp when the voltage of the primary lamp circuit exceeds a threshold voltage.
Implementations may include one or more of the following features. For example, the primary lamp circuit may include an impedance element in series connection with a discharge lamp. The impedance element may be a ballast capacitor or a ballast reactor.
The primary lamp circuit also may include a high intensity discharge lamp, such as a gas vapor lamp. The auxiliary lamp may be an incandescent lamp.
The auxiliary controller may have output leads that are connected to the auxiliary lamp. The auxiliary controller also may have input leads that are connected across the impedance element.
In another general aspect, an auxiliary controller for a lighting system includes a power supply circuit, a switching circuit, and a coupling circuit that connects the power supply circuit to the switching circuit. The power supply circuit has input and output voltages and the switching circuit has open and closed states. An increase in the input voltage beyond a certain threshold causes an increase in the output voltage that biases the switching circuit in the open state.
The power supply circuit may have input terminals for connection to an alternating current voltage. An impedance capacitor may be connected in series with one of the input terminals to provide impedance to the alternating current voltage. A diode bridge may be connected to the impedance capacitor and to the input terminals. The diode bridge may produce unfiltered direct current voltage from the alternating current voltage.
A filter capacitor may be connected across the diode bridge to remove ripple voltages and produces a steady direct current voltage. A zener diode may be connected across the filter capacitor to clamp the direct current voltage to a predetermined level. Output terminals may be connected across the zener diode, and a current limiting resistor may be connected in series with the output terminals.
The coupling circuit of the auxiliary controller may have an optically isolated triac that has open and closed states. Increasing the power supply circuit input voltage above a threshold voltage may increase the power supply output voltage to bias the optically isolated triac in the closed state.
The switching circuit of the auxiliary controller may have a voltage divider that is connected to the coupling circuit. A triac may be connected to the voltage divider by a diac. The triac may be triggered into conduction when a breakover voltage on the diac is exceeded.
In another general aspect, operating a lighting system includes providing a primary lamp circuit, providing an auxiliary lamp circuit, connecting an auxiliary controller between the primary lamp circuit and the auxiliary lamp circuit, sensing a primary lamp circuit voltage, and extinguishing an auxiliary lamp when the primary lamp circuit voltage exceeds a threshold voltage. The primary lamp circuit, the auxiliary lamp circuit, and the auxiliary controller may have some or all of the features described above.
The current implementation eliminates the need for a current transformer from the auxiliary lighting system, which can reduce costs, weight, and bulk, and can improve performance.
The details of one or more implementations are set forth in the drawings and the description. Other features and advantages will be apparent from the description, including the drawings and the claims.